Effect of Christmas Island rock phosphate and rice straw compost application on soil phosphorus availability and maize (Zea mays L.) growth in a tropical acid soil of Kelantan, Malaysia

Phosphorus (P) fixation is very common in Malaysian acid soils due to the fixation of soluble inorganic P by Al and Fe under acidic soil pH conditions. Farmers tend to perform lots of liming and apply excess amount of P fertilizers in order to saturate the Al and Fe in the soil so that the plants are able to absorb the remaining P. Excessive liming and application of P fertilizers are not only not economical but also not environmentally friendly. Compost with a large surface area and pool of negative charges could be used to reduce P fixation in acidic soil. Hence, this study was carried out to assess the effect of amending Christmas Island rock phosphate (CIRP) with rice straw (RS) compost in improving soil P availability, nutrient uptake, and dry matter production of maize cultivated on a Malaysian tropical acid soil. A pot experiment was carried out in this study with the use of maize (FI hybrid sweet corn 801) as a test crop. The chemical properties of soils applied with RS compost were significantly improved (P ≤ 0.05) compared to treatments without RS compost. As the soil pH increased, there was significant reduction in exchangeable acidity, Al and Fe in soil due to exchangeable Al and Fe were fixed with negatively charged functional groups of RS compost’s surfaces, thus increased the P availability and exchangeable cations in the soil applied with RS compost. There was also significantly higher N, P, and K uptake in leaf, stem, and root of maize in the treatments applied with RS compost. Application of CIRP with RS compost was found to increase the soil P availability, maize nutrient uptake, and dry matter production at the end of the pot experiment. An application rate of 15–20 t ha⁻¹ of RS compost together with 130 kg ha⁻¹ urea, 200 kg ha⁻¹ CIRP, and 67 kg ha⁻¹ muriate of potash is recommended to improve the soil NPK contents and growth of Zea mays in acidic soil.